The present invention relates to non-return valve having a valve housing, in which is formed a flow channel which possesses a vertical channel section, having an inlet aperture and an outlet aperture and having a blocking device for closing the flow channel, which blocking device comprises a valve seat surrounding the outlet aperture of the vertical channel section and a valve disc, which is movable in the valve housing in the vertical direction between an open position and a closed position in which sealing surfaces on the valve disc and valve seat come into sealing contact, wherein the valve disc is movably guided in the valve housing via at least one guide surface provided on its outer circumference and comprises flow apertures radially outside its sealing surface.
Non-return valves of this type are known in for example from DE-OS 14 50 483 and are fitted in fluid-carrying lines to ensure that a fluid in the line can flow only in one direction.
The conventional non-return valves have undoubtedly proved their value in practice. However, it is regarded as a partial problem that the conventional valve discs are complex in construction and, because of the large number of parts, have only limited suitability for xe2x80x9csterilexe2x80x9d applications.
It is therefore an object of the invention to provide a non-return valve of the type specified initially which possesses a simple construction and guarantees a maximum level of sterility.
This object is achieved, according to the invention, in that the valve disc possesses a diameter that, starting from its guide surface, becomes smaller towards the valve seat, forming an inclined external surface, and that the flow apertures, which are formed as bores in the valve disc start from the inclined external surface and converge in the direction facing away from the sealing surface and are disposed in a uniform distribution over the circumference of the valve disc.
The valve with the inventive valve disc has a simple design and possesses a diameter that, starting from its guide surface, becomes smaller towards the bottom, forming an inclined external surface, in other words it tapers towards its underside. This measure not only permits a saving of weight but also improves the flow conditions for the fluid on opening of the valve, because it can more easily pass the valve disc to reach the flow apertures. For example, the valve disc can narrow conically downwards, starting from its guide surface, in which case the angle of the conical external surface to the horizontal is preferably approximately 45xc2x0. Alternatively, however, the external surface may also be of curved configuration, for example narrowing convexly downwards starting from the guide surface.
Since the flow apertures in the valve disc to start from the inclined external surface and converge obliquely upwards, in which case they are expediently inclined relative to the axis of the valve disc at an angle of from 30 to 60xc2x0, in particular 45xc2x0, the flow properties of the non-return valve can be optimized by these measures.
If a non-return valve is used in which the valve disc is movable in the valve housing between an upper, open position and a lower, closed position, the valve disc according to a preferred embodiment can be urged into its closed position by gravity alone, so that additional restoring means in the form of restoring springs or the like, such as are provided in the prior art, become superfluous and the number of components is thus further reduced.
If, in this embodiment, a fluid such as, for example, water flows through the non-return valve in operation, the valve disc is lifted in the vertical direction, when the incoming pressure is sufficiently high, so that the fluid can flow through the flow apertures of the valve disc. With increasing incoming pressure, the flow rate will also increase until the non-return valve is fully opened. During the opening process, the behaviour of the pressure and the opening of the valve are not necessarily in proportion but are stable. When the incoming pressure is reduced, the non-return valve closes. Backflow of the medium is thus avoided.
The level of incoming pressure under which the non-return valve according to the invention opens is essentially dependent on the weight of the valve disc and the prevailing force of gravity. As a rule, it is desirable for the valve to open and medium to be allowed through even at low incoming pressures of, for example, 0.02 bar.
According to an embodiment of the invention, provision is made for the guide surface to be formed on the upper edge region of the valve disc. In this case, the guide surface can form a continuous guide edge. This, however, is not absolutely necessary. For example, it is also possible for the flow apertures to be open towards the edge of the valve disc and for the guide surface thus to be interrupted by the flow apertures.
The flow apertures can, in principle, be of any desired configuration. In order to achieve the most uniform possible distribution of forces, according to a preferred embodiment, provision is made for the flow apertures to be disposed with a uniform distribution over the circumference of the valve disc. In this case, the flow apertures can be formed, for example, as bores, which are easy to produce.
The valve discs and valve seat can be formed to provide a metallic seal, in order words formed as appropriately smooth metal surfaces. According to a preferred embodiment, however, provision is made for one of the sealing surfaces to be formed on an elastic packing ring which is inserted, for example, into an annular groove on the underside of the valve disc. The packing ring may consist, for example, of rubber having a Shore hardness of 80.
In a further development of this embodiment, provision may be made for the packing ring to taper towards the sealing surface. In particular, the packing ring may possess a trapezoidal cross section, on whose short side the sealing surface is formed.
To ensure a high level of sterility, the valve disc and/or the valve housing is or are expediently produced from stainless steel, and the surfaces coming into contact with the fluid, especially the surface of the valve disc, may be polished, especially electropolished.
According to a preferred embodiment of the invention, the valve housing consists of a lower housing portion with the vertical channel section and the valve seat and an upper housing portion with a flow chamber which is open towards the underside and in which the valve disc is movably guided. The valve seat and the flow chamber thus lie, as it were, in the plane of separation of the valve housing and can be easily worked upon and installed.
In a conventional manner, the lower housing portion and the upper housing portion are releasably connected to one another and centred relative to one another. To produce the connection, connecting flanges having mutually corresponding through bores for connecting screws may be provided in a conventional manner on the housing portions.
The flow chamber naturally possesses a significantly larger diameter than the vertical channel section which is shut off by the valve disc, and a channel section adjoining the flow chamber at the top will also possess a significantly smaller diameter than the flow chamber. In this case, expediently, the transition region between the flow chamber and the channel section adjoining the latter at the top is configured to narrow conically, and the angle of the transition region to the horizontal should be from 30 to 60xc2x0.
Moreover, according to an advantageous embodiment of the invention, it is envisaged that the bottom of the flow chamber slopes down towards the valve seat at an angle of inclination of from 1.5 to 4xc2x0, especially 2xc2x0, starting from the wall on which the valve disc is guided. This ensures that no fluid can accumulate in the corner region between the flow chamber wall and the flow chamber bottom.
In a further embodiment of the invention, it is envisaged that an inlet channel section, particularly a horizontal inlet channel section, is formed in the lower housing portion and is connected to the flow chamber via the vertical channel section.
As an alternative to the embodiment described above, in which a channel section adjoins the flow chamber at the top, it is also possible to provide for an outlet channel section, in particular a horizontal outlet channel section, to be formed in the lower housing portion and to be connected via the flow chamber to the inlet channel section. In this embodiment, then, the inlet channel section and the outlet channel section of the non-return valve are formed in the lower housing portion and connected to one another via the flow chamber lying above them in the upper housing portion, in which flow chamber the valve disc is also disposed. In this case, the valve seat is formed, in part, on a housing partition separating the inlet channel section from the outlet channel section. Furthermore, an outflow channel surrounding the valve seat and open towards the outlet channel section may be formed between the lower housing portion and the upper housing portion, which outflow channel, in particular, is open at its upper side facing towards the flow chamber and possesses a depth that increases towards the outlet channel section, so that fluid in the outflow channel automatically flows down into the outlet channel section.
In the case of non-return valves in which the valve disc is movable vertically in the valve housing between a lower, open position and an upper, closed position, the valve disc may in principle be formed in the same manner as in the embodiments described above, with the proviso that in this case it is installed by a reversed installation procedure, in other words with the sealing surface facing upwards. Additional measures are necessary, however, to press the valve disc into its upper, closed position. For this purpose, it is possible, first, for the valve disc to be supported at its underside by a spring element which presses it into its closed position. Alternatively, the valve disc may consist of polytetrafluoroethylene (Teflon), in which case it is then pressed into its upper, closed position solely by the buoyancy of the fluid in the flow channel.